Siemens SIMATIC S7-200 System Manual page 325

Embedded Variables in Text and SMS Messages
The Modem module can embed data values from the CPU in the text messages and format the
data values based on a specification in the message. You can specify the number of digits to the
left and right of the decimal point, and whether the decimal point is a period or a comma. When
the user program commands the Modem module to transmit a text message, the Modem module
retrieves the message from the CPU, determines what CPU values are needed within the
message, retrieves those values from the CPU, and then formats and place the values within the
text message before transmitting the message to the service provider.
The telephone number of the messaging provider, the message, and the variables embedded
within the message are read from the CPU over multiple CPU scan cycles. Your program should
not modify telephone numbers or messages while a message is being sent. The variables
embedded within a message can continue to be updated during the sending of a message. If a
message contains multiple variables, those variables are read over multiple scan cycles of the
CPU. If you want all of the embedded variables within a message to be consistent, the you must
not change any of the embedded variables after you send a message.
Data Transfers
The Modem module allows your program to transfer data to another CPU or to a Modbus device
over the telephone line. The data transfers and telephone numbers are configured with the
Modem Expansion wizard, and are stored in the Modem module configuration block. The
configuration block is then downloaded to the data block in the S7-200 CPU. The Modem
Expansion wizard also creates program code to allow your program to initiate the data transfers.
A data transfer can be either a request to read data from a remote device, or a request to write
data to a remote device. A data transfer can read or write between 1 and 100 words of data. Data
transfers move data to or from the V memory of the attached CPU.
The Modem Expansion wizard allows you to create a data transfer consisting of a single read from
the remote device, a single write to the remote device, or both a read from and a write to the
remote device.
Data transfers use the configured protocol of the Modem module. If the Modem module is
configured to support PPI protocol (where it responds to STEP 7--Micro/WIN), the Modem module
uses the PPI protocol to transfer data. If the Modem module is configured to support the Modbus
RTU protocol, data transfers are transmitted using the Modbus protocol.
The telephone number of the remote device, the data transfer request and the data being
transferred are read from the CPU over multiple CPU scan cycles. Your program should not
modify telephone numbers or messages while a message is being sent. Also, you should not
modify the data being transferred while a message is being sent.
If the remote device is another Modem module, the password function can be used by the data
transfers by entering the password of the remote Modem module in the telephone number
configuration. The callback function cannot be used with data transfers.
Password Protection
The password security of the Modem module is optional and is enabled with the Modem
Expansion wizard. The password used by the Modem module is not the same as the CPU
password. The Modem module password is a separate 8-character password that the caller must
supply to the Modem module before being allowed access to the attached CPU. The password is
stored in the V memory of the CPU as part of the Modem module configuration block. The Modem
module configuration block must be downloaded to the data block of the attached CPU.
If the CPU has the password security enabled in the System Data Block, the caller must supply
the CPU password to gain access to any password protected functions.
Creating a Program for the Modem Module Chapter 10
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